Something just went down on Jupiter. Monday morning, at 11:35:30 UT, amateur astronomers glimpsed a brief but blazing flash of light in the upper reaches of the planet's cloudy atmosphere. If past observations are any indication, Jupiter may have just sustained a major impact event. If that's the case, the gas giant may have just saved Earth from a devastating cosmic collision.

The first report of the "impact flash" is believed to have come from amateur astronomer Dan Petersen, who described his observation in a post to CloudyNights.com:

This morning (9/10/2012) at 11:35:30 UT, I observed a bright white two second long explosion just inside Jupiter's eastern limb, located at about Longitude 1 = 335, and Latitude = + 12 degrees north, inside the southern edge of the NEB [aka the planet's North Equatorial Belt]. This flash appeared to be about 100 miles in diameter. I used my Meade 12 LX200 GPS telescope and a binoviewer working at 400X for the observation, seeing was very good at the time.

Amateur astronomer George Hall was actually filming Jupiter when the flash occurred. On Hall's website, he describes happening upon Peterson's forum post, and deciding to go back and examine the videos he had collected early yesterday morning. The image featured up top (and again, below, without text), is a screenshot from the footage that he captured. A video of the impact is featured below, as well.

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"We'll have to wait and see if a dark spot develops inside the southern regions of the NEB over the next day or two," writes Peterson in his forum post. These spots, according to Cosmic Log's Alan Boyle, would be "a sure sign" that an asteroid or comet had been drawn to the planet by its strong gravitational tug. But here's something I was surprised by: according to Boyle, Jupiter may have just saved Earth — or some other planet — from its own impact event. This is the third time since 2009 amateur astronomers have witnessed an impact flash on Jupiter. The massive gas giant, which exerts considerable gravitational pull, is something of a cosmic whipping boy in our solar system, regularly shielding inner planets like Earth from potential collisions. Writes Boyle:

Jupiter impacts are of great interest to astronomers, amateur and professional, because they're part of the orbital billiards game that has shaped our solar system. In some cases, the cosmic interloper is destroyed before it has any visible effect on Jupiter's cloud tops. In weightier cases, the object breaks up and leaves black marks on the planet's atmosphere. The case of Comet Shoemaker-Levy 9 in 1994 is the most notable in recent memory.

Beyond the planetary science, there's the "phew" factor: Astronomers suspect that giant Jupiter's gravitational pull serves as a cosmic shield, sweeping up incoming objects that would have a deadlier effect if they were to slam into our planet. Some scientists say that without Jupiter, life on Earth wouldn't have had much of a chance.

Pretty wild, right? According to Boyle, we probably wont know how big the impact object was until astronomers have had a closer look at any aftermath visible in Jupiter's clouds; but for now, let's be glad this flash happened on Jupiter, and not here on Earth.